The actress, who briefly appears in the movie as Mera, queen of Atlantis, talked to E! News' WillMarfuggi about joining the superhero film franchise at its premiere in Hollywood last night.

"It's kind of weird. This is my first time stepping into this universe; my first superhero role was Justice League. I have a small part in this amazing, huge, big collection of all the superheroes," said Heard, who modeled an Atelier Versace dress and wore Christian Louboutin heels. "We followed it up with Aquaman, which we just wrapped up a week ago. I feel incredibly lucky for this to be my entrance into this world. I'm learning the best part of it all is, really, the fans. Better than all the superpowers and all the super personalities that embody them, the fans who love it, and the energy behind it—that's been the most rewarding, amazing surprise of it all."

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As Jason Momoa would agree, getting in fighting form for Aquaman (in theaters Dec. 21, 2018) required months of preparation. "Let's just say I missed chocolate so much," Heard said. "But now I'm wrapped, so it's back on, chocolate!" The shoot presented other challenges for the cast, as half the movie was shot on land, while the rest was shot underwater. "The last four or five months of shooting, I didn't have a dry day. I trained for about six months beforehand. A lot of diet, exercise, taking care of yourself—being in the best shape that you can be," she said. In the end, the training paid off, and Heard felt stronger than ever before. "When your physical strength is elevated," she explained, "I don't see how your internal strength cannot follow suit."

Principal photography began in Australia in May, and days were often long on set. "It's hard being away from home. It's hard being away from the ones you love," Heard said. "It's hard living and maintaining a normal life when you're that far away for that long. Eight months doing anything is tough. So that was an exercise in patience, stamina and fortitude, but I made it!"